 |
|
Workers inspect a rooftop PV installation. Improper handling, storage, or installation of the PV panels can cause damage to the roof. |
The popularity of rooftop photovoltaic (PV) panels has exploded during the past decade as Building Teams look to maximize building energy efficiency, implement renewable energy measures, and achieve green building certification for their projects.
However, installing rooftop PV systems—rack-mounted, roof-bearing, or fully integrated systems—requires careful consideration to avoid damaging the roof system. Improper handling, storage, or installation of the PV panels can cause damage to the roof, which can lead to moisture intrusion, wind uplift problems, and even structural damage. In addition, rooftop PV systems should be designed with future maintenance, roof repairs, and fire-suppression efforts in mind.
BD+C asked a pair of top-notch roofing experts to identify the most critical design, construction, and installation considerations. They offer the following tips:
 |
|
Photovoltaic arrays should be confi gured to allow access for future maintenance, roof repairs, and fire-suppression efforts. |
1. Verify the fire rating of your rooftop photovoltaic system.Most rooftop PV systems qualify for a Class C fire rating, while most of the roof coverings over which these systems are installed are fire rated Class A or B, says Philip D. Dregger, PE, RRC, principal with roof and waterproofing consultant Technical Roof Services Inc., Concord, Calif.
Dregger says the fire rating, especially spread of flame, is critical, especially for roof-bearing and rack-mounted systems. For instance, Building Teams may need to take steps like incorporating half-inch gypsum board into the assembly to obtain the proper fire rating.
For sloped roofs, Dregger says it is especially important to confirm that the required fire classification is available at the slope required. “For instance, standing-seam metal roofs routinely qualify as Class A fire-resistant on unlimited slopes, whereas the same standing-seam metal roofs covered with thin-film, flexible PV panels have significant slope restrictions,” he says.
2. Flashing detail is critical for maintaining the warranty. Flashing detail work must be performed by a contractor approved by the roof membrane manufacturer, says Mike Ennis, technical director of the Single Ply Roofing Industry (SPRI), Waltham, Mass., which recently convened a task force to identify key rooftop PV installation issues. “It's not so much a difference in the details as it is that the details are properly completed,” says Ennis.
Building owners must get such permission in advance from the roofing manufacturer or the warranty may be voided. The main concern, says Ennis, is keeping a record of alterations to the roof system. “For example, if a manufacturer gets a leak call immediately after an alternation is completed, they know where to start looking for the leak,” he says.
3. PV systems must be properly marked. Marking is needed to provide emergency responders with appropriate warning and guidance with respect to working around and isolating the solar electric system. Proper marking helps responders identify energized electrical lines that connect the solar modules to the inverter, according to the California Department of Forestry and Fire Protection's (CDFFP) Solar Photovoltaic Installation Guideline (www.osfm.fire.ca.gov/pdf/reports/solarphotovoltaicguideline.pdf).
Materials used for marking must be weather resistant and should be placed adjacent to the main service disconnect in a location clearly visible from the location where the lever is operated.
4. Make sure to protect the roof system while handling PV panels. Damage to roof systems, especially single-ply membranes, often occurs during the handling of the PV panels. SPRI's Ennis offers four tips for avoiding roof system damage while moving and storing PVs:
-
Store boxed PV units over joists to avoid deflecting the metal deck.
-
If boxed units are palletized, place a cushion layer of plywood between the pallet and the roof surface.
-
Do not point-load the roof surface by placing the corner of a hard panel directly on the surface.
-
Use moving equipment fitted with pneumatic tires to transport equipment and materials over the finished roof surface.
5. In retrofit projects, consider roof life before installing PVs. Due to potentially high costs associated with temporarily disconnecting and moving PV panels to execute roof repairs, Building Teams should assess the remaining life of the existing roof covering as part of a PV project, says Dregger.
He says serious consideration should be given to replacing the existing roof covering as part of a PV project. At the very least, says Dregger, you should investigate and repair roof leaks and perform any preventive maintenance work, even if it is not scheduled to be performed for a couple of years.
6. Pay close attention to the location of direct current (DC) conductors. Conduit, wiring systems, and raceways for photovoltaic circuits should be located as close as possible to the ridge or hip or valley and from the hip or valley as directly as possible to an outside wall to reduce trip hazards and maximize ventilation opportunities, according to the CDFFP's installation guidelines.
DC combiner boxes should be located such that conduit runs are minimized in the pathways between arrays. To limit the hazard of cutting live conduit in venting operations, DC wiring should be run in metallic conduit or raceways when located within enclosed spaces in a building and should be run (to the maximum extent possible) along the bottom of load-bearing members.
7. Provide for fall protection in certain cases. In retrofit projects, if the PV modules direct foot traffic to within six feet of unprotected roof edges or roof openings, fall protection provisions, such as guardrails and roof hatches, are a must, says Dregger.
8. Configure PV arrays to allow access for future maintenance, roof repairs, and fire-suppression efforts. CDFFP's installation guidelines recommend a minimum of six feet of clearance along the perimeter of the roof and at least four feet around roof access hatches and skylights. Also, pathways should be provided along the centerline of both axes of the roof. Locate these pathways over structural members.
9. Make sure integrated PV panels can handle high winds. For semi-rigid PV panels adhered over mechanically attached single-ply roofs, make sure that the PV panels can accommodate billowing of the singly-ply membrane during high-wind conditions without incurring damage, such as cracking, splitting, or rupture. Dregger recommends installing air retarders and supplemental membrane fasteners around each PV panel to help avoid damage.
Related Stories
| Feb 11, 2011
Kentucky’s first green adaptive reuse project earns Platinum
(FER) studio, Inglewood, Calif., converted a 115-year-old former dry goods store in Louisville, Ky., into a 10,175-sf mixed-use commercial building earned LEED Platinum and holds the distinction of being the state’s first adaptive reuse project to earn any LEED rating. The facility, located in the East Market District, houses a gallery, event space, offices, conference space, and a restaurant. Sustainable elements that helped the building reach its top LEED rating include xeriscaping, a green roof, rainwater collection and reuse, 12 geothermal wells, 81 solar panels, a 1,100-gallon ice storage system (off-grid energy efficiency is 68%) and the reuse and recycling of construction materials. Local firm Peters Construction served as GC.
| Feb 11, 2011
Justice center on Fall River harbor serves up daylight, sustainable elements, including eucalyptus millwork
Located on historic South Main Street in Fall River, Mass., the Fall River Justice Center opened last fall to serve as the city’s Superior and District Courts building. The $85 million facility was designed by Boston-based Finegold Alexander + Associates Inc., with Dimeo Construction as CM and Arup as MEP. The 154,000-sf courthouse contains nine courtrooms, a law library, and a detention area. Most of the floors have the same ceiling height, which will makes them easier to reconfigure in the future as space needs change. Designed to achieve LEED Silver, the facility’s elliptical design offers abundant natural daylight and views of the harbor. Renewable eucalyptus millwork is one of the sustainable features.
| Feb 11, 2011
Chicago high-rise mixes condos with classrooms for Art Institute students
The Legacy at Millennium Park is a 72-story, mixed-use complex that rises high above Chicago’s Michigan Avenue. The glass tower, designed by Solomon Cordwell Buenz, is mostly residential, but also includes 41,000 sf of classroom space for the School of the Art Institute of Chicago and another 7,400 sf of retail space. The building’s 355 one-, two-, three-, and four-bedroom condominiums range from 875 sf to 9,300 sf, and there are seven levels of parking. Sky patios on the 15th, 42nd, and 60th floors give owners outdoor access and views of Lake Michigan.
| Feb 11, 2011
Grocery store anchors shopping center in Miami arts/entertainment district
18Biscayne is a 57,200-sf urban retail center being developed in downtown Miami by commercial real estate firm Stiles. Construction on the three-story center is being fast-tracked for completion in early 2012. The project is anchored by a 49,200-sf Publix market with bakery, pharmacy, and café with outdoor seating. An additional 8,000 sf of retail space will front Biscayne Boulevard. The complex is in close proximity to the Adrienne Arsht Center for the Performing Arts, the downtown Miami entertainment district, and the Omni neighborhood, one of the city’s fast-growing residential areas.
| Feb 11, 2011
Chicago architecture firm planning one of China’s tallest towers
Chicago-based Goettsch Partners was commissioned by developer Guangzhou R&F Properties Co. Ltd. to design a new 294,570-sm mixed-use tower in Tianjin, China. The Tianjin R&F Guangdong Tower will be located within the city’s newly planned business district, and at 439 meters it will be one of China’s tallest buildings. The massive complex will feature 134,900 sm of Class A office space, a 400-key, five-star hotel, 55 condominiums, and 8,550 sm of retail space. The architects are designing the tower with multi-story atriums and a high-performance curtain wall to bring daylight deep into the building, thereby creating deeper lease spans. The project is currently finishing design.
| Feb 11, 2011
Two projects seek to reinvigorate Los Angeles County medical center
HMC Architects designed two new buildings for the Los Angeles County Martin Luther King, Jr., Medical Center as part of a $360 million plan to reinvigorate the campus. The buildings include a 120-bed hospital, which involves renovation of an existing tower and several support buildings, and the construction of a new multi-service ambulatory care center. The new facilities will have large expanses of glass at all waiting and public areas for unobstructed views of downtown Los Angeles. A curved glass entrance canopy will unite the two buildings. When both projects are completed—the hospital in 2012 and the ambulatory care center in 2013—the campus will have added more than 460,000 sf of space. The hospital will seek LEED certification, while the ambulatory care center is targeting LEED Silver.
| Feb 11, 2011
Sustainable community center to serve Angelinos in need
Harbor Interfaith Services, a nonprofit serving the homeless and working poor in the Harbor Area and South Bay communities of Los Angeles, engaged Withee Malcolm Architects to design a new 15,000-sf family resource center. The architects, who are working pro bono for the initial phase, created a family-centered design that consolidates all programs into a single building. The new three-story space will house a resource center, food pantry, nursery and pre-school, and administrative offices, plus indoor and outdoor play spaces and underground parking. The building’s scale and setbacks will help it blend with its residential neighbors, while its low-flow fixtures, low-VOC and recycled materials, and energy-efficient mechanical equipment and appliances will help it earn LEED certification.
| Feb 11, 2011
Texas megachurch inspired by yesteryear’s materials, today’s design vocabulary
The third phase of The First Baptist Church of Pasadena, Texas, involves construction of a new 115,000-sf worship center addition. Currently in design by Zeigler Cooper, the project will include a 2,500-seat worship center (with circular layout and space for a 50-person orchestra and 200-person choir), a 500-seat chapel (for weddings, funerals, and special events), and a prayer room. The addition will connect to the existing church and create a Christian Commons for education, administration, music, and fellowship. The church asked for a modern design that uses traditional materials, such as stone, brick, and stained glass. Construction is scheduled to begin this summer.
| Feb 11, 2011
Apartment complex caters to University of Minnesota students
Twin Cities firm Elness Swenson Graham Architects designed the new Stadium Village Flats, in the University of Minnesota’s East Bank Campus, with students in mind. The $30 million, six-story residential/retail complex will include 120 furnished apartments with fitness rooms and lounges on each floor. More than 5,000 sf of first-floor retail space and two levels of below-ground parking will complete the complex. Opus AE Group Inc., based in Minneapolis, will provide structural engineering services.
| Feb 11, 2011
Four-story library at Salem State will hold half a million—get this—books!
Salem State University in Massachusetts broke ground on a new library and learning center in December. The new four-story library will include instructional labs, group study rooms, and a testing center. The modern, 124,000-sf design by Boston-based Shepley Bulfinch includes space for 500,000 books and study space for up to a thousand students. Sustainable features include geothermal heating and cooling, rainwater harvesting, and low-flow plumbing fixtures.
